Use pm2 and specify node version using –interpreter flag with node version absolute path:
sudo pm2 start app.js --interpreter=/home/ken/.nvm/v4.4.2/bin/node
or
sudo pm2 start app.js --interpreter=/home/ken/.nvm/v7.4.0/bin/node
etc..
If you change the node version wherever I mentioned --interpreter="***.." the app will run in exact node version.
Once you completed the above approach to verify use following command
sudo pm2 show 'app name'